Understanding Tall Fescue

Tall fescue is an extremely hardy, well-adapted grass species used for hay and pasture in the central and eastern United States and the Pacific Northwest. Although tall fescue has gotten a bad reputation in the horse industry, it is a safe and practical grass for most classes of horses with the exception of broodmares.

A Kentucky field full of tall fescue.

There are many varieties of tall fescue from all over the world, but the variety most commonly found in Central Kentucky and the Eastern U.S. is called Kentucky 31 (KY-31). This variety now occurs naturally across the eastern part of the country based on extensive plantings for erosion control and pasture in the 1940s and '50s. It is usually infected with a microscopic endophytic fungus called Neotyphodium coenophialum, which lives inside the plant. The endophyte produces chemicals (alkaloids) that benefit the plant by making tall fescue tolerant of heavy grazing as well as drought, disease, and insect damage. However, ergovaline, one particular alkaloid produced by infected fescue, has been shown to cause adverse effects in broodmares and possibly stallions including abortion, foaling difficulty, lack of milk production, and reduced ejaculate volume. These issues and related health problems are collectively termed fescue toxicosis.

Tall Fescue for Pleasure Horses
While grazing infected tall fescue is risky for breeding stock, no adverse effects have been reported in non-breeding horses. Tall fescue is not only a high-quality forage, but it will also continue to survive and provide forage during very stressful conditions, such as drought and overgrazing. If farm owners wish to graze breeding stock, there are other, non-toxic tall fescue varieties available.

Novel and Endophyte-Free Tall Fescue
Many non-infected tall fescue varieties have been identified, propagated, and are available commercially as endophyte-free tall fescue. These varieties are safe for all classes of horses. However, endophyte-free tall fescue varieties do not have the robustness of KY-31, especially in the southern U.S., since they do not produce any alkaloids.

Recently, researchers have discovered other types of endophytes that produce only beneficial alkaloids, but not the harmful ergovaline. Tall fescue varieties infected with these novel, or friendly, fungi are termed "novel endophyte-infected tall fescue" and are now commercially available and safe for all classes of horses. Consumers should double-check the variety description to ensure the variety they are buying for any breeding stock produces no ergovaline.

Novel or endophyte-free tall fescue varieties are excellent choices for horse farms that breed or wish to breed in the future.

Other Tall Fescues in the News
A recent article on The Horse discussed a Mediterranean-type tall fescue with a specific strain of endophyte causing a syndrome in horses called equine fescue edema. While this is a serious concern in other countries, virtually all tall fescue varieties in the United States are Continental-type, not Mediterranean-type, and do not cause this syndrome.

Things to Remember about Tall Fescue

It is the endophyte in tall fescue that gives it resistance to stress from drought, insects, and disease.

Tall fescue itself is not dangerous, but ergovaline produced by the endophyte that often infects tall fescue can cause health concerns in breeding mares and stallions grazing infected tall fescue pastures.

Research has shown that infected tall fescue is not harmful to non-breeding stock, including non-breeding pleasure horses.

Novel endophyte-infected or endophyte-free tall fescues are safe for all classes of horses.

The recently reported Mediterranean-type tall fescue is dangerous to horses, but it is rarely planted in the United States and therefore is not a concern for U.S. horse owners.

By Ray Smith, Krista Cotten, and Laura Schwer, the University of Kentucky

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